The interaction between lining materials and composite resin restorative materials

Cavity Bases Revisited

OBJECTIVE

The aim of this paper was to review the current literature on cavity bases while focusing on the role of zinc oxide eugenol (ZOE) and resin-modified glass ionomers (RMGI) as cavity bases.

MATERIALS AND METHODS

A thorough literature search between 1970 and 2020 was done using Scopus, PubMed, and Google Scholar databases. The keywords of the search strategy were as below: cavity liners and bases, pulp protection, zinc oxide eugenol, and resin-modified glass ionomer. No specific inclusion or exclusion criteria were applied as to what articles would be included in this review.

CONCLUSION

This review emphasizes that the available literature provides very little evidence to support the routine use of a base under amalgam or composite restorations. This review favors the adoption of "no more lining or bases" in shallow and moderate cavity preparations. However, an exception might be a "protective base" of RMGI following the application of calcium hydroxide (CH) liners in deep cavities. Bonded RMGIs are suitable cavity base materials and should always replace zinc oxide eugenol bases in daily practice.

The Effect of Temporary Cement Cleaning Methods on the Retention of Crowns

PURPOSE

To evaluate the effect of temporary cement cleaning methods on the retention of cemented crowns using zinc phosphate cement and resin-modified glass ionomer cement.

MATERIALS AND METHODS

Forty titanium specimens were fabricated to simulate prepared molars with minimally retentive taper. The Ni-Cr cast crowns were fabricated, temporarily cemented, and separated. The specimens were divided into four groups according to the temporary cement cleaning method (n = 10) as follows: control group (no temporary cementation), orange solvent group, ultrasonic cleaning group, and air-abrasion group. After the cleaning procedures, the specimens were cemented with definitive cements (zinc phosphate cement and resin-modified glass ionomer, RMGI, cement) and subjected to thermocycling (5000 cycles, 5-55°C, dwell time, 10 seconds). The tensile bond strength of each specimen was measured using a universal testing machine, and the results were analyzed using the Kruskal-Wallis and Mann-Whitney U test (α = 0.05).

RESULTS

When cemented with zinc phosphate cement, the statistical analysis showed that the value of the air-abrasion group was significantly higher than those of the other groups (p < 0.01). There was no statistically significant difference among the other groups. When cemented with RMGI cement, the air-abrasion group showed the lowest value, and the control group showed the highest value (p < 0.01). The difference between the ultrasonic cleaning group and the orange solvent group was not statistically significant.

CONCLUSION

The use of temporary cement did not have a significant influence on retention of permanently cemented crowns when zinc phosphate cement was used for permanent cementation. Airborne-particle abrasion after provisional cementation improved retention of crowns cemented with zinc phosphate cement; however, the use of temporary cement significantly decreased retention of permanently cemented crowns when RMGI cement was used regardless of the temporary cement cleaning method.

Cavity Adaptation of Water-Based Restoratives Placed as Liners under a Resin Composite

Purpose. To investigate the cavity adaptation of mineral trioxide (ProRoot MTA/MT), tricalcium silicate (Biodentine/BD), and glass ionomer (Equia Fil/EF) cements used as liners and the interfacial integrity between those liners and a composite resin placed as the main restorative material. Materials and Methods. Standardized class I cavities (n: 8 per group) were prepared in upper premolars. Cavities were lined with a 1 mm thick layer of each of the tested materials and restored with Optibond FL adhesive and Herculite Precis composite resin. Cavity adaptation of the restorations was investigated by computerized X-ray microtomography. The regions of interest (ROI) were set at the cavity-liner (CL) interface and the liner-resin (LR) interface. The percentage void volume fraction (%VVF) in the ROI was calculated. The specimens were then sectioned and the interfaces were evaluated by reflection optical microscopy, to measure the % length (%LD) of the interfacial gaps. Selected samples were further evaluated by scanning electron microscopy. Statistical analysis was performed by two-way ANOVA and Student-Newman-Keuls multiple comparison test (a = 0.05). Results. MT showed significantly higher %VVF and %LD values in CL interfaces than BD and EF (p < 0.05). No significant differences were found among the materials for the same values at the LR interfaces. Conclusions. When used as a composite liner, ProRoot MTA showed inferior cavity adaptation at dentin/liner interface when compared to Biodentine and Equia Fil.

The Influence of Zinc Oxide Eugenol (ZOE) and Glass Ionomer (GI) Base Materials on the Microhardness of Various Composite and GI Restorative Materials

Objective:

Re-examining the well accepted concept that Zinc-Oxide-Eugenol bases (ZOE) have a negative effect on composite restoration materials microhardness, in light of the advancement in composite materials and newer publications.

Methods:

Five modern composite restoration materials were used, including hybrid (Xtra-fill and Z250), micro-fill hybrid (G-aenial and Gradia-direct) and methacrylate-free restorative material (Silorane- oxirane). Two base materials were used IRM (ZOE-base) and Fuji-IX (GI-base). Samples were made using a designed mold, in which composite discs were cured on top and in close relation to base materials. Micro-hardness testing was performed using a DMH-2 microhardness tester utilizing the Knoop method.

Results:

Statistic analysis demonstrated significantly better microhardness of three composite materials when IRM was used as base in comparison to control (G-aenial, Gradia direct and Filtek silorane), and no differences in two materials (Filtek universal Z250 and Voco Xtra-fil). Fuji-IX bases showed a significant positive effect on the microhardness of four composite materials, and a negative effect on one material (Voco Xtra-fill). In comparison with other tested restoration materials, both Voco Xtra-fill and Fuji-IX showed higher microhardness results (P<0.05).

Significance:

Related to microhardness, both ZOE and GI bases can be used safely as bases under composite restorations. The results of this study together with the results published recently showed that the concept of not using ZOE or GI bases under composite must be reconsidered. Fuji IX showed microhardness results similar to the best composite material and therefore it can be used as a restorative material.

A comparison of retentive strength of implant cement depending on various methods of removing provisional cement from implant abutment

PURPOSE

This study evaluated the effectiveness of various methods for removing provisional cement from implant abutments, and what effect these methods have on the retention of prosthesis during the definitive cementation.

MATERIALS AND METHODS

Forty implant fixture analogues and abutments were embedded in resin blocks. Forty cast crowns were fabricated and divided into 4 groups each containing 10 implants. Group A was cemented directly with the definitive cement (Cem-Implant). The remainder were cemented with provisional cement (Temp-Bond NE), and classified according to the method for cleaning the abutments. Group B used a plastic curette and wet gauze, Group C used a rubber cup and pumice, and Group D used an airborne particle abrasion technique. The abutments were observed using a stereomicroscope after removing the provisional cement. The tensile bond strength was measured after the definitive cementation. Statistical analysis was performed using one-way analysis of variance test (α=.05).

RESULTS

Group B clearly showed provisional cement remaining, whereas the other groups showed almost no cement. Groups A and B showed a relatively smooth surface. More roughness was observed in Group C, and apparent roughness was noted in Group D. The tensile bond strength tests revealed Group D to have significantly the highest tensile bond strength followed in order by Groups C, A and B.

CONCLUSION

A plastic curette and wet gauze alone cannot effectively remove the residual provisional cement on the abutment. The definitive retention increased when the abutments were treated with rubber cup/pumice or airborne particle abraded to remove the provisional cement.

In vitro inhibitory effect of clove essential oil and its two active principles on tooth decalcification by apple juice

The dental erosion or decalcification of enamel is a significant clinical problem. Apple acidic beverages are thought to increase the potential for dental erosion. The purpose of this in vitro study was to investigate the effect of clove essential oil (CEO) and its active principles on tooth decalcification of apple juices. On GC-MS analysis, CEO showed a high content of eugenol (58.29%) and eugenyl acetate (19.10%). Teeth specimens were randomly divided into 5 treatment groups: control, CEO, eugenol, eugenyl-acetate, and fluoride. The specimens were exposed for 24 h and were analyzed for calcium contents using Inductively Coupled Plasma with Optical Emission Spectroscopy (ICP-OES). Data were analyzed using student t-test (P < 0.05). CEO, eugenol, and eugenyl-acetate significantly decreased the decalcification of tooth by the apple juice to only 17, 24, and 21 mgL⁻¹, respectively. Hemolytic activity on human erythrocytes was studied to exclude the possibility of further associated cytotoxicity. It was observed that the CEO and its two lead molecules inhibit the decalcification and/or promote the remineralization caused by the apple juices. The effect of the test compounds appears to be distinct like that of fluoride treatment. CEO may, therefore, serve to be a promising adjunct to fluoride in the treatment of root caries during minimally invasive therapy.

Effect of the dentin cleansing techniques on dentin wetting and on the bond strength of a resin luting agent

STATEMENT OF PROBLEM

Remnants of the provisional cement on prepared teeth may have an adverse effect on the performance of the definitive luting agent.

PURPOSE

This in vitro study investigated the effect of different dentin cleansing techniques on the bond strength of a resin luting agent and dentin wetting.

MATERIAL AND METHODS

Sixty buccal or lingual coronal portions of human molar teeth were mounted, with the buccal or lingual surfaces up, in acrylic resin blocks. The specimens were prepared until the dentin was exposed and a eugenol-containing provisional cement (Temp Bond) was applied to the dentin surfaces. After mechanical removal of the cement with a carving instrument, specimens were divided into 6 groups of 10 specimens each. The dentin surfaces of the specimens were treated with 1 of 5 cleansing techniques: Group S, cleansing agent (Sikko Tim); Group C, cleansing agent (Cavity Cleanser); Group O, rotary instrumentation (OptiClean); Group OS, rotary instrument preceding Sikko Tim; and Group OC, rotary instrumentation preceding Cavity Cleanser. The remaning 10 specimens were untreated and served as controls (CT). An adhesive resin luting agent (Variolink II) was applied to all specimens. Shear bond strength (MPa) was measured using a universal testing machine at a 0.5 mm/min crosshead speed. To measure the contact angle, another 6 groups (n=5) were prepared using the same methods. Contact angle measurements were performed to assess wettability using the Axisymmetric Drop Shape Analysis-Contact Diameter (ADSA-CD) technique. Wettability measurements were made with water. Data were statistically analyzed by 1-way analysis of variance with Tukey HSD tests (alpha=.05). The effect of the dentin cleansing techniques on removing the provisional cement from the dentin surface was examined with scanning electron microscope (SEM).

RESULTS

Specimens cleaned with all techniques showed stronger shear bond strength values than control specimens (P<.001), with the exception of C specimens. The surface cleansing techniques tested affected the dentin wetting significantly in comparison with the control group (P<.001), except for the C and the O groups. There was no significant difference in wetting between the groups C and O. The SEM observations demonstrated that the dentin cleansing techniques left differing amounts of provisional cement remnants.

CONCLUSION

Specimens treated with only the cleansing agent Sikko Tim showed the highest bond strength, likely due to the solvent effect of Sikko Tim on the removal of provisional cement. The lowest bond strength was obtained with the rotary instrument. It was concluded that the provisional cement could plug the dentinal tubules into which the resin luting agent penetrates.

The effects of eugenol and epoxy-resin on the strength of a hybrid composite resin

The compatibility of different dental materials (root canal sealer and composite core build-up restoratives) is an important factor for a successful restoration. The aim of this in vitro study was to determine the effects on compressive and diametral tensile strength of a classical chemical cure composite resin (Henry Schein Composite Anterior-Posterior dental restorative) when in contact with either eugenol or an epoxy-resin (EZ-Fill) in a variety of situations: (a) eugenol or epoxy-resin added during mixing of a composite resin before curing; (b) vapor exposure to cured samples; and (c) specimens placed directly in eugenol or epoxy-resin (after curing). Compressive strengths and diametral tensile strengths were tested for each group. Only the addition of eugenol during mixing with the composite resin (directly before curing) resulted in specimens that were unable to be tested, because they did not achieve a full cure or hardness. For all other groups, there were no significant differences with respect to either compressive strength (p = 0.17) or diametral tensile strength (p = 0.39). Group 1 (mixed directly with eugenol) was found to be statistically different from groups 2 through 7.

The effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials to dentin

PURPOSE

This study investigated the effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials (FluoroCore and Ti-Core) to dentin.

MATERIALS AND METHODS

Dentin was exposed in three groups of extracted teeth (20 specimens each). In group one, dentin was covered with eugenol-containing temporary cement; the second group was covered with eugenol-free temporary cement; and the third group was left uncovered and served as a control group. All specimens were stored for 1 week at 37 degrees C and 100% humidity. The dentin surfaces were cleaned and treated using the GLUMA adhesive system, followed by placement of composite core build-ups. Debonding of the core material was accomplished using the Accuforce Elite test system.

RESULTS

There was a significant reduction in bond strength for the specimens covered with eugenol temporary cement (p < .0001), but no significant difference was found between the control group and the group treated with eugenol-free temporary cement. Bond strength of the Ti-Core material to dentin was significantly higher than that of FluoroCore (p < .0001).

CONCLUSION

Pretreatment of the dentin with eugenol-based temporary cement adversely affects the bond strength of resin composite core material to dentin.

Effect of phenolic compounds on the polymerization of methyl methacrylate

The inhibitory effects of six phenolic compounds and two analogues on the polymerization of methyl methacrylate (MMA) by azobisisobutyronitrile (AIBM) were examined. Differential scanning calorimetry was used to determine the induction period (IP) and initial rate of polymerization (IRP). The IP values (minutes) decreased in the order: eugenol > thymol > hydroquinone > cresol > guaiacol > phenol >>> safrole > methol. The IRP values of all compounds tested ranged from 0.8 to 1.2 percent per minute, except for hydroquinone (0.2 percent per minute). Phenolic compounds inhibited the polymerization of MMA by scavenging radicals, and eugenol was the most potent inhibitor.